/* 广告 */
body,html{
    width: 100%;
    height: 100%;
}
body{
    background-image: url('../img/advertisement-bg.jpg');
    background-repeat: no-repeat;
    background-size: cover;
    background-position: center top;
}
.berder_nav{
    height: 40px;
    background-color: #fff;
    text-align: center;
    line-height: 40px;
}
/* 时间盒子 */
.big_box{
    display: flex;
    justify-content: flex-end;
}
.time_box{
    width: 105px;
    height: 40px;
    background-color: #fff;
    text-align: center;
    line-height: 40px;
    border-radius: 20px;
    margin-top: 20px;
    margin-right: 20px;
}
// 字体动画
@keyframes run{
    0%  {transform: translateY(-200px);opacity: 0;}
    100%  {transform: translateY(0px);opacity: 1;}
}
.footer{
    margin-top: 100%;
}
.txt_key{
    opacity: 1;
    text-align: center;
    animation: run 3s;
}